This invention relates to a process and apparatus for the low-temperature separation of air into dry product gases wherein at least a portion of the entering air is cooled by heat exchange against at least one of the product gases and is freed of impurities by an adsorption process prior to this heat exchange.
Such a process is utilized in all those cases wherein a large portion of the product gases nitrogen and oxygen is desired in the pure condition. In such an instance, the amount of purge gasrquired to resublime the impurities frozen out in the primary heat exchanger (reversing exchangers or regenerators) is not available. Consequently, the necessity arises to purify at least a portion of the entering air in an adsorption process.
In conventional methods of this type, a molecular sieve is ordinarily utilized as the adsorber. Apart from the fact that the molecular sieves are very expensive, disturbances in the operation within the molecular sieve unit frequently result in congealed deposits clogging the heat exchanger for the entering air, thereby causing plant shutdown.